The present invention is generally directed to fluid distribution member assemblies for use in plasma processing apparatuses, and more particularly, to mitigating the effects of thermal stress on fluid distribution member assemblies during plasma processing.
Currently, Integrated Circuit (IC) development requires driving plasma ashing processes to utilize increasingly aggressive gas chemistry and thermal environments. It is important that the ashing process occur at a uniform rate across the surface of a wafer being processed. To this end, process conditions are precisely controlled and carefully engineered components are used in the processing chamber to insure uniform ashing. One such component is a so-called baffle plate, or fluid distribution plate and/or assemblies designed to uniformly direct and distribute energized plasma onto a wafer surface. One exemplary fluid distribution plate design is shown and described in U.S. Patent Application Publication No. 2005/0241767.
The plasma temperature within dry asher systems is generally in the range of 1000° C. Molecular species are excited within the microwave source of the system and carry energy downstream. Energy is transferred in the form of heat to plasma wetted parts. As a consequence of uneven heat transfer, thermal non-uniformities develop across these parts and give rise to internal stresses which in turn compromise their structural integrity. Surface recombination of species upon collision with various components within the processing system including, in particular, the fluid distribution member, which causes extremely high heat loads, requiring novel thermal management of the design of the plasma processing system including the fluid distribution member.
Glasses, Ceramics and Fused Silica are often employed for the design of parts used in the most critical areas of plasma processing systems, including the fluid distribution member due to their resistance to high temperatures as well as their chemical purity. Stress fracture often occurs in these materials due to uneven thermal loading or differential expansion between dissimilar materials. Uneven heating and cooling can in many cases generate stresses in excess of the material's yield or ultimate tensile stress limit, resulting in catastrophic failure. Although impervious to high temperatures in the general range of plasma processing, these materials are sensitive to substantial temperature gradients and thermal shock.
Fluid distribution members and/or assemblies used in plasma systems may be comprised of alumina ceramic (AL2O3), Fused silica (SiO2), or other glasses, ceramics, metals, or any suitable materials and/or combinations thereof. Downstream microwave plasma sources, akin to plasma torches, output radicalized gas and cause extreme temperature gradients on parts impinged upon. Further temperature differences between a center and edge of a first plate to be contacted by plasma ranges within hundreds of degrees Celsius. This gradient can generate significant thermal stress to cause failure of the plate. According to conventional processes, segmenting fluid distribution plates into concentrically nested structures has proven to be a relatively effective form of interrupting the gradients and therefore reduce the internal stresses, while maintaining process uniformity. This, however, increases the cost of parts significantly and may lead to particles due to sliding between the segmented plates. Further, with increasing power requirements there may be a necessity for further plate optimization for a best geometry configuration of nested plates.
Accordingly, there is a need in the art for an improved fluid distribution member and/or assembly that maintains plasma or gas uniformity and can withstand the various conditions utilized during high temperature plasma or gas processes (e.g., withstanding wide thermal gradients and related stresses, and/or are economically viable, and/or are compatible with a plurality of chemistries, and/or the like).